In the clinical chemistry analysis of, for example, cholesterol, triglycerides, glycemia, transaminase, it is important that readouts can be carried out on different samples treated as homogeneously as possible especially as far as the times of mixing the sample with the reagents and the temperatures of the sample under test and those of the reagent are concerned. It is also desirable to carry out surveys, that is, detections like photometric readouts in very short and closely spaced time intervals, to ensure in particular the homogeneity of the data taken from a number of sequentially tested samples.